'\" te
.\"  Copyright (c) 2005, Sun Microsystems, Inc.  All Rights Reserved
.\" The contents of this file are subject to the terms of the Common Development and Distribution License (the "License").  You may not use this file except in compliance with the License.
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.TH CRYPT 1 "Mar 8, 2005"
.SH NAME
crypt \- encode or decode a file
.SH SYNOPSIS
.LP
.nf
\fBcrypt\fR [\fIpassword\fR]
.fi

.SH DESCRIPTION
.sp
.LP
The \fBcrypt\fR utility encrypts and decrypts the contents of a file.
\fBcrypt\fR reads from the standard input and writes on the standard output.
The \fIpassword\fR is a key that selects a particular transformation. If no
\fIpassword\fR is given, \fBcrypt\fR demands a key from the terminal and turns
off printing while the key is being typed in. \fBcrypt\fR encrypts and decrypts
with the same key:
.sp
.in +2
.nf
example% \fBcrypt key < clear.file > encrypted.file\fR
example% \fBcrypt key < encrypted.file | pr\fR
.fi
.in -2
.sp

.sp
.LP
prints the contents of \fBclear.file\fR.
.sp
.LP
Files encrypted by \fBcrypt\fR are compatible with those treated by the editors
\fBed\fR(1), \fBex\fR(1), and \fBvi\fR(1) in encryption mode.
.sp
.LP
The security of encrypted files depends on three factors:  the fundamental
method must be hard to solve; direct search of the key space must be
infeasible; "sneak paths" by which keys or cleartext can become visible must be
minimized.
.sp
.LP
\fBcrypt\fR implements a one-rotor machine designed along the lines of the
German Enigma, but with a 256-element rotor.  Methods of attack on such
machines are widely known, thus \fBcrypt\fR provides minimal security.
.sp
.LP
The transformation of a key into the internal settings of the machine is
deliberately designed to be expensive, that is, to take a substantial fraction
of a second to compute.  However, if keys are restricted to (say) three
lower-case letters, then encrypted files can be read by expending only a
substantial fraction of five minutes of machine time.
.sp
.LP
Since the key is an argument to the \fBcrypt\fR command, it is potentially
visible to users executing \fBps\fR(1) or a derivative command. To minimize
this possibility, \fBcrypt\fR takes care to destroy any record of the key
immediately upon entry. No doubt the choice of keys and key security are the
most vulnerable aspect of \fBcrypt\fR.
.SH FILES
.sp
.ne 2
.na
\fB\fB/dev/tty\fR\fR
.ad
.RS 12n
for typed key
.RE

.SH SEE ALSO
.sp
.LP
.BR des (1),
.BR ed (1),
.BR ex (1),
.BR ps (1),
.BR vi (1),
.BR attributes (7)
